Sinusitis is a common problem associated with significant patient morbidity, lost productivity and cost. Accurate diagnosis of bacterial disease is not possible in the ambulatory setting, and antibiotics are overused. There are few studies that assess the effectiveness of antibiotic therapy, and study inclusion criteria severely limit the generalizability of their findings to inform primary care management. To reduce the excessive use of antibiotics, the Centers for Disease Control and Prevention (CDC) and an expert panel recommended that 1) antibiotic treatment be reserved for patients with moderate or severe symptoms that persist for at least seven days and include maxillary or facial pain and purulent nasal secretions, and 2) initial antibiotic treatment be a narrow-spectrum drug. The effectiveness of these treatment recommendations has not been evaluated. The objective of this study is to determine the incremental benefit of amoxicillin added to a regimen of symptomatic treatments in patients diagnosed with acute bacterial rhinosinusitis using clinical criteria. We will conduct a.double-blinded, randomized, placebo-controlled trial in the primary care setting. Two hundred adult patients who meet the CDC recommended diagnostic criteria for acute bacterial rhinosinusitis will be randomized to receive a 10-day course of either amoxicillin or placebo. In addition, all patients will receive symptomatic treatments including an analgesic, an oral decongestant and an anti-tussive agent. Patient outcomes will be assessed by telephone interview at 3, 7, 10 and 28 days. The primary outcome measures will be the effect of treatment on the disease-specific quality of life, measured with a validated evaluative instrument, the Sino-Nasal Outcome Test-16 (SNOT-16). Secondary outcomes will include the effect of treatment on change in functional status and symptoms, disease recurrence, satisfaction with care and the direct costs of treatment. We propose the current study as the first in a series of studies designed to determine the most effective primary care management of patients with acute rhinosinusitis. We will evaluate symptomatic treatments in future studies. The relevance of this research to public health is that it will provide knowledge about how to best care for patients with acute sinusitis, a common problem that is cared for in the community. In addition, knowledge gained from this research could be used to decrease the inappropriate use of antibiotics. [unreadable] [unreadable]